1. Field of the Invention
The present invention generally relates to communication networks, and more particularly, the present invention relates to a signal packet relay device which receives and transmits data packets in a communications network.
A claim of priority is made to Japanese patent application number 2008-080370, filed Mar. 26, 2008, the disclosure of which is incorporated herein by reference.
2. Description of the Related Art
Weighted Random Early Detection (WRED) is a queue management system utilized to reduce the number of re-sent signal packets on communications networks such as the internet, thereby reducing traffic congestion on the network. According to WRED, a minimum delete threshold and a maximum delete threshold are established in advance. So long as the number of stored signal packets in the queue at any given time is less than the minimum delete threshold, all received and stored signal packets are maintained. However, if the number of stored signal packets exceeds the minimum delete threshold, incoming signal packets may be deleted (dropped) according a delete probability (drop probability) which corresponds to the number of the signal packets stored in the queue. If the number of stored packets exceeds the maximum delete threshold, all incoming signal packets are deleted.
FIG. 12 graphically illustrates WRED packet delete probabilities. As shown, delete probability is zero so long as the number of the signal packets stored in the queue is less than the minimum delete threshold. Then, in this example, the delete probability increases linearly between the minimum delete probability and the maximum delete probability. If the number of signal packets stored in the queue exceeds the maximum delete probability, then the delete probability of incoming signal packets becomes 100 percent (i.e., all incoming signal packets are deleted).
In an effort to increase operational speeds relative to devices relying partially on software executions, Japanese Patent Application Laid-Open Publication No. 2005-94392, describes a hardware-implemented packet processing device for avoiding congestion of communication network traffic by signal packet deletion. This document acknowledges that an ideal delete probability K1 between a minimum delete threshold to a maximum delete threshold is substantially linear. However, the signal packet processing device proposed by the document describes a non-linear implementation in which the section between the minimum delete threshold and the maximum delete threshold is divided into multiple step-increased subsections, where each of the subsection has a constant delete probability. This non-linear increase in delete probability can adversely impact characteristics of the WRED implementation.